Drinking more coffee might lower your risk for type 2 diabetes, a new large U.S. study suggests.

People who boosted their daily java intake by more than one cup over four years reduced their diabetes risk, while adults who drank less coffee saw their odds for diabetes rise, the study of 123,000 adults found.

"It looks like there is a dose-response relationship between increasing coffee consumption and a lower risk of diabetes," said lead researcher Dr. Frank Hu, professor of nutrition and epidemiology at the Harvard School of Public Health.

"Basically, the more coffee, the lower the risk of diabetes," Hu said. "People who drink three to five cups of coffee a day enjoyed a significant reduction in type 2 diabetes risk."

However, people can drink too much coffee, particularly those who don't respond well to caffeine, Hu cautioned. Caffeine, a stimulant, keeps some people awake, and can also cause the heart to speed up.

"It's hard to pinpoint which components of coffee may contribute to a decreased risk of type 2 diabetes," Hu said. "Current thinking is that it is the combination of antioxidants and other nutrients."

The study, published online April 24 in Diabetologia, shows an association between more coffee and lower diabetes risk but can't actually prove that one causes the other, Hu said. However, experiments in animals and a small human trial did find a cause-and-effect relationship between coffee and reduced insulin resistance, he said. Insulin resistance is a warning sign of diabetes.

Coffee can be part of a healthy diet, but people shouldn't look to it as a way to prevent type 2 diabetes, Hu said. "People should still watch their weight and be physically active," he added.

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